1. Field of the Invention
The present invention relates generally to spinal fixation devices and more specifically relates to a pedicle screw system having an improved screwdriver coupling interface and securing of the screwdriver to the polyaxial screw assembly.
2. Description of the Related Art
The spinal column is a highly complex system of bones and connective tissues that provides support for the body and protects the delicate spinal cord and nerves. There are many types of spinal column disorders including scoliosis (abnormal lateral curvature of the spine), kyphosis (abnormal forward curvature of the spine, usually in the thoracic spine), excess lordosis (abnormal backward curvature of the spine, usually in the lumbar spine), spondylolisthesis (forward displacement of one vertebra over another, usually in a lumbar or cervical spine) and other disorders caused by abnormalities, disease or trauma, such as ruptured or slipped discs, degenerative disc disease, fractured vertebra, and the like. Patients that suffer from such conditions usually experience extreme and debilitating pain, as well as diminished nerve function.
A technique commonly referred to as spinal fixation is employed for fusing together and/or mechanically immobilizing vertebrae of the spine. Spinal fixation may also be used to alter the alignment of adjacent vertebrae relative to one another so as to change the overall alignment of the spine. Such techniques have been used effectively to treat the above-described conditions and, in most cases, to relieve pain suffered by the patient. Spinal fixation often involves use of polyaxial pedicle screws fixed to the vertebrae. However, there are some disadvantages associated with current pedicle screws and polyaxial screwdrivers used to install them. There remains room for improvement in the manner of engaging the screw head, the complexity of use, the required manipulation of the many parts associated with some complex devices and improved screw loading during installation.